JP6725418B2 - Method and apparatus for manufacturing hot formed wheel discs - Google Patents

Description

The present invention relates to a method for manufacturing a wheel disc of a wheel, wherein the wheel disc is manufactured by hot forming from a blank composed of steel, the blank being at least partly during or after hot forming. Hardened, preferably press hardened, the blank is hot formed using at least one punch and at least one die and at least one opening is introduced into the blank using hot trimming means. The invention further relates to a device for manufacturing a wheel disc from a blank made of steel, the device being suitable for performing hot forming of the blank to provide a wheel disc, and Having at least one punch for forming and at least one die, means are provided for performing hot trimming to introduce at least one opening into the blank.

The wheels of a vehicle are safety-critical components and therefore have to be able to withstand permanently the mechanical loads that are subject to high fluctuations during operation. A conventional steel wheel is composed of a wheel disc that secures a connection with a wheel hub and a wheel rim band that holds a tire. Wheel discs are currently manufactured by cold forming in a multi-stage press with up to 11 stages. Only cold-formable microalloy duplex stainless steels with a strength of 400 to 600 MPa are used here. Apart from the service life of steel wheels, weight also plays an important role, in particular material cost, unsprung mass, rotational inertia and thus fuel consumption. In principle, it is possible to use materials of high strength, for example materials of high vibration resistance. However, as the strength of the steel material increases, the degree of formability of the material generally decreases, so it seems unlikely that the cold-formable material will have a lightweight construction. By utilizing hot forming, it is possible to obtain a component that simultaneously satisfies the requirements for high formability and has very high strength and dimensional accuracy. When performing hot forming, it is preferable to heat the blank to a temperature at which the forming behavior is significantly improved. For example, significant improvements in molding are obtained during structural conversion to an austenitic structure. Therefore, it is necessary to heat the blank to a temperature above the _Ac1 temperature point, which depends on the composition of the steel. The excellent formability of the material during hot forming can significantly reduce many of the forming steps required for cold forming, especially when the steel material has an austenitic structure. In this regard, as many forming or machining steps as possible can be replaced by tools, thus eliminating subsequent work. However, there is the problem that various perforations, which cannot be introduced into the blank before hot forming, have to be provided during the manufacture of the wheel disc. Until now, such perforations had to be introduced after the component has been hardened and tempered, but if the material thickness exceeds, for example, 3 mm, the perforations can only be made by laser cutting. In general, the openings in the wheel disc, for example the wheel bolt holes, must have a high dimensional accuracy, so these holes cannot be introduced before hot forming. In addition, a standard shape for receiving the wheel bolt is also required. The introduction of holes into the wheel disc after hot forming is associated with great expense. This also applies, for example, to the subsequent laser cutting of the holes, since the subsequent mechanical trimming involves considerable wear.

Going back to the Applicant, DE 103 23 833 A1 discloses manufacturing wheel discs from tempered steel, for example from 22MnB5 type manganese boron steel, by hot forming. The manufacture of a sheet metal element, at least a plurality of areas of which has been hardened and which is manufactured from a sheet metal blank and has at least one opening with a protruding ring, is further described in DE 10201011117066A1. Are known.

With this as a starting point, the invention is based on the object of defining a method for manufacturing a wheel disc of a wheel, which method is used to further reduce the weight of the wheel disc and to meet the required shape and safety requirements. As realized, the wheel disc can be manufactured easily with high precision. Furthermore, the object of the invention is to propose a device for carrying out the method according to the invention.

According to a first teaching of the invention, the object indicated is a method for manufacturing a wheel disc of a wheel, wherein at least one opening is introduced during hot trimming with at least one trimming bolt and an application bolt. And the application bolt has at least one region having a cross-sectional shape that varies in the longitudinal direction of the application bolt, and the application bolt adjusts the at least one opening via the variation cross-sectional shape.

It has been found that even the trimming of blanks during hot forming to introduce openings into the hot formed wheel discs significantly reduces tool wear during hot trimming, and thus Mechanical trimming can be both low cost and low cost. Furthermore, an applied bolt having a varying cross-sectional shape in at least the area can be adjusted immediately after trimming the introduced opening. It is also possible here to carry out this adjustment in a warm state, ie at an elevated temperature, for example above the _MS starting point, which depends on the composition of the steel, and can be used in such a way that less force is required. Massive shaping and adjustment can be done simultaneously on the open area by using an application bolt. Here, massive forming is to be understood as meaning, for example, upset or forging.

The sheet metal thickness of the initial blank is, for example, in the range of 1 mm to 7 mm, preferably in the range of 2 mm to 5 mm, so that the weight can be further reduced. The sheet metal thickness can be reduced by selecting a material having high strength. Especially when using manganese boron steel, also called tempered steel, hot forming gives rise to the possibility of simultaneously achieving at least hardening or press hardening in several areas, so that the finished wheel disc is lightweight and high. It will have strength. The hot trimming and hot forming are preferably completed before the actual press hardening.

According to a first refinement of the method according to the invention, at least one trimming bolt and at least one applying bolt are used for hot trimming wheel bolt holes, vent holes and/or wheel hub holes of a wheel disc. To introduce. All three types of holes must meet high accuracy requirements and be less susceptible to cracking. When using the method according to the invention, there is the option of subjecting the area of the cutting edge of the opening to a massive molding, so that the risk of cracking in the opening area is reduced. Furthermore, a particularly smooth opening edge can be obtained by massive molding without finishing work.

The costs for manufacturing wheel discs are further reduced by hot forming and hot trimming the blank to provide the wheel discs in one working stroke. In particular, the use of the trimming bolt and the application bolt according to the invention makes it possible to carry out the method in one operating step or operating stroke.

According to a further refinement of the method according to the invention, at least one hollow application bolt, into which the corresponding trimming bolt penetrates during hot trimming, is used. First, a particularly durable cutting edge can be provided by the applied bolt. Second, it may move to remove trimmed material. Furthermore, the hollow application bolts and the corresponding counter-trimming bolts can couple the trimming with the movement of the punch and/or die, for example.

According to a further refinement of the method, the cutting edge of the opening is at least partially formed by massive molding. For example, the required shape of a conical or spherical countersunk wheel bolt hole can be easily created by at least partial massive molding. Furthermore, the corresponding opening edge reduces the risk of cracking in the opening area and ensures the required rigidity of the opening.

According to the following variation, when hot trimming is performed by cutting out the trimmed material downwards, gravity can be used to easily remove and move the trimmed material.

According to a further refinement of the method, simple push-in guide means can be used in the device for hot forming of blanks, at least to ensure a path of movement of the trimming bolt and at least one application bolt. The path of travel of the one trimming bolt and the at least one application bolt is coupled to the path of travel of the punch and/or die.

Alternatively, for example, it is at least partly possible that the movement path of the at least one trimming bolt and the at least one application bolt operates separately from the movement path of the punch and/or the die. This movement can be done hydraulically, pneumatically, or servo-electrically, for example, and to some extent allows a high degree of flexibility regarding the time and the position of the tool for performing hot trimming. According to a further refinement of the method, the formed blank can be cut to perform hot forming integral with hot trimming to provide a wheel disc without the use of holddown means. Particularly preferred. As a result, the material supply during molding is minimized, so that the molding force during hot forming is further reduced.

Finally, according to a further embodiment of the method, a blank of composite material of manganese boron steel, multiphase steel or multi-layer steel is hot formed to provide a wheel disc. Manganese boron steel, and other tempered steels, can be press hardened after hot forming, which results in particularly high strength. This also applies to multiphase steels and corresponding composites of hardenable or press hardenable steels.

According to a further teaching of the method, the object indicated is realized by an apparatus for manufacturing a wheel disc, which is provided with at least one trimming bolt and at least one corresponding application bolt, which application bolt is of said application bolt. Means are provided for adjusting the opening with at least one region having a longitudinally varying cross-sectional shape, the region of the application bolt having a varying cross-sectional shape.

As already mentioned above, a device that provides hot forming and has an integrated trimming bolt and application bolt simultaneously realizes the hot forming and trimming of a blank or a hot formed wheel disc, resulting in a forming force. In addition to lowering, the high precision opening in the wheel disc can be made at the same time. Push-in guide means can be provided, for example, as means for adjusting the opening using the varying cross-sectional area of the applied bolt, which push-in guide means during the closing process of the device and when the punch is pulled into the die. The applicable bolt can be moved correspondingly.

At least one application bolt is preferably of hollow design so that the corresponding trimming bolt can penetrate into the application bolt. By the penetration of the trimming bolt into the application bolt, the movement of the trimming bolt and the application bolt of the tool can easily be achieved via simple push-in guide means. In particular, this configuration also offers the advantage of performing hot forming of the blank to provide the wheel disc and hot trimming in one operating cycle. For example, application bolts of hollow design, for example, have a particularly high rigidity, so that application bolts can provide high-strength cutting edges.

When the trimming bolts are arranged such that at least one trimming bolt penetrates into the corresponding applying bolt from above, the trimmed material of the blank produced by the trimming bolt is removed from the area of the device through the corresponding applying bolt. can do. In particular, gravity can automatically move the trimmed material out of the area of the device.

Finally, means may be provided for connecting the movement control of the trimming bolt and the application bolt with the movement path of the punch and/or the die, or a means for controlling the movement of the trimming bolt, the application bolt, the punch and/or the die separately. Can be provided. The movement control coupled, for example via push-in guide means, improves the process reliability by means of a particularly simple arrangement for the movement control of the trimming bolt, the application bolt and the punch and/or the die. On the other hand, alternatives that provide separate movement control of the trimming bolts, application bolts, punches and/or dies provide a great deal of flexibility regarding the preparation of specific working steps during the manufacture of the wheel disc. For example, the timing at which the trimming bolt enters the applicable bolt or the timing at which trimming is performed by punching can be controlled separately.

The present invention is described in detail below with reference to the exemplary embodiments with reference to the drawings.
FIG. 1 shows a perspective view of a vehicle wheel. FIG. 2 shows the wheel disc of the wheel in front view. 3-5 show in schematic cross-sections an exemplary embodiment of an apparatus for manufacturing a wheel disc from a blank at three different points in the method. 3-5 show in schematic cross-sections an exemplary embodiment of an apparatus for manufacturing a wheel disc from a blank at three different points in the method. 3-5 show in schematic cross-sections an exemplary embodiment of an apparatus for manufacturing a wheel disc from a blank at three different points in the method. 6-8 show in schematic cross-sections the interaction of the trimming bolt and the application bolt in carrying out the method. 6-8 show in schematic cross-sections the interaction of the trimming bolt and the application bolt in carrying out the method. 6-8 show in schematic cross-sections the interaction of the trimming bolt and the application bolt when carrying out the method.

First of all, FIG. 1 diagrammatically shows a general wheel composed of a wheel disc 1 and a wheel rim band 2. The wheel disc 1 is connected to the wheel rim band 2 so as to be in close contact with each other, and the force of the wheel hub is transmitted to the wheel rim band 2.

FIG. 2 shows the wheel disc 1 in a front view. You can see the three types of openings that the wheel disc 1 has. Initially, the wheel hub hole 3 is centrally located and is surrounded by a total of five concentrically arranged wheel bolt holes 4. Ventilation holes 5 necessary for the ventilation of the brakes are additionally provided in the outer area of the wheel disc. If the dimensional tolerance is exceeded, the wheel disc 1 becomes unstable, for example, when the wheel is used. Therefore, the wheel hub hole 3, the wheel bolt hole 4, and the ventilation hole 5 are extremely accurate. Must be introduced to.

FIGS. 3, 4 and 5 then show a method of manufacturing a wheel disc for a wheel at three different times, the blank 6 being shown only in FIG. 3 for convenience. This blank 6 is heated, for example, to a temperature above the _Ac1 temperature point of the material and placed in the device shown in FIG. In this state, an austenite structure, which has a good influence on the degree of formability, appears mainly. The apparatus comprises a punch 7 and a die 8 which are used to hot form the blank 6. Hot forming is generally carried out at elevated temperatures, i.e. when the blank has, for example, an austenitic structure which guarantees suitable forming conditions.

FIG. 3 further shows the trimming bolt 9 and the application bolt 10, which has a hollow design and has a region 10a in which the cross-sectional shape of the application bolt 10 changes. As shown in FIG. 4, over the course of this method, the punch 7 penetrates into the opening provided in the die 8 and consequently punches out, for example, the axle receiving hole 3 of the wheel disc. In FIG. 4, the trimming bolt 9 is, for example, located on the blank and has not yet cut the blank. However, this trimming time can in principle be chosen at will. A trimming bolt 9 is then introduced into the application bolt 10 and the blank 6 not shown in FIGS. 4 and 5 trims the area so that wheel bolt holes result. In FIG. 5, for example, the trimming bolt penetrates into the applicable bolt. The applied bolt 10 further has a region 10a having a varying cross-sectional shape. Therefore, the cross section of the applied bolt increases vertically downwards in this region.

The actual hot-trimming when hot-forming the forming blank 6 will be described in detail with reference to FIGS. 6 to 8 show the trimming area 11 enlarged and extracted by the apparatus shown in FIGS. 3 to 5.

FIG. 6 illustrates a trimming bolt 9, a hot forming blank 6 and an application bolt 10 according to the exemplary embodiment of FIGS. At the point in this method shown in FIG. 6, the trimming bolts are placed on the blank 6 and have moved further in the direction of the application bolts. As shown in FIG. 7, a trimming bolt penetrates, for example, into the apply bolt 10 and moves the trimmed material from the forming area through the apply bolt. The trimming bolt preferably moves the material of the trimmed blank 6 from the forming area in the downward gravity direction. After trimming the opening, the application bolt 10 moves vertically upwards, so that the area with the varying cross-sectional shape 10a adjusts the opening of the blank 6. For example, as shown in FIG. 8, during adjustment, the opening area can be thickened or a conical or spherical counterbore can be formed. For example, the edge 6a of the opening region of the blank 6 can be thickened. By thickening or flattening the surface of the cutting edge, the opening has strong strength and resistance to cracking. Furthermore, further requirements imposed on the rigidity of the wheel discs can also be brought about by the variable shaping of the applied bolts, for example by massive shaping, forging or upsetting. In addition, the remaining area of the die or punch 7 can provide massive shaping in adjusting the opening.

The blank 6 preferably has a thickness of 2 mm to 7 mm, particularly preferably 3 mm to 5 mm. Significantly thicker wall thicknesses may be required for wheel discs provided for track wheels.

Using the principle of the method shown in FIGS. 6 to 8, not only can the wheel bolt holes 4 of the wheel disc 1 be introduced, but also the central wheel hub hole and the vent hole can be incorporated in the wheel disc. As can be seen with reference to FIGS. 6 to 8, the hot forming and hot trimming of the blank 6 is preferably performed in a single operating step.

The trimming bolts, application bolts, punches and means for controlling the path of travel of the die are not shown in FIGS. 3-5 and 6-8. However, it is readily conceivable that the timing of trimming or adjusting the individual openings can be selected with high flexibility if the movement paths of the trimming bolt, the application bolt, the punch and the die are actuated separately. In order to control the path of movement of the trimming bolt, the application bolt, the punch and the die in a particularly simple manner, it is also possible to provide simple motion coupling means, for example push-in guide means. The push-in type guide means is extremely robust, but can provide a highly accurate movement path.

Due to the high temperature of the formed blanks, the forming forces during hot forming and hot trimming are relatively low, for example relative to the strength after the wheel disc press hardened in multiple areas. In this respect, it is possible to find the possibility of further weight savings by means of a wheel disc manufactured by the method according to the invention, without giving up a relatively easy and cost-effective manufacturing method.

Claims (16)

A method of manufacturing a wheel disc for a wheel, the wheel disc being manufactured from a blank made of steel by hot forming, the blank being at least partially cured during or after the hot forming, In the method, the blank is hot formed using at least one punch and at least one die and at least one opening is introduced into the blank using hot trimming means.
At least one opening is introduced during said hot trimming with at least one trimming bolt and an application bolt,
The applied bolt has at least one region having a cross-sectional shape that gradually decreases in diameter toward the distal end side in the longitudinal direction of the applied bolt, and using the applied bolt, the at least one opening is formed. Edges of the at least one region and the at least one punch are plastically deformed and compressed, whereby parts other than the compressed part of the at least one opening are plastically deformed and thickened. ,
A method characterized by that. The method of claim 1, wherein at least one trimming bolt and at least one application bolt are used to introduce wheel bolt holes, vent holes, and/or wheel hub holes of the wheel disc during the hot trimming. A method characterized by being performed. Method according to claim 1 or 2, characterized in that hot forming and hot trimming of the blank are carried out in one working stroke. Method according to any one of claims 1 to 3, characterized in that during the hot trimming, at least one hollow application bolt is used into which the corresponding trimming bolt penetrates. A method according to any one of claims 1 to 4, characterized in that the cutting edge of the opening is at least partially formed by massive molding. A method according to any one of claims 1 to 5, characterized in that the hot trimming is performed by cutting out the trimmed material downwards. Method according to any one of claims 1 to 6, characterized in that the movement path of the at least one trimming bolt and the at least one application bolt is connected to the movement path of the punch and/or the die. And how to. Method according to any one of claims 1 to 6 , wherein the travel path of the at least one trimming bolt and the at least one application bolt operates independently of the travel path of the punch and/or the die. A method characterized by that. A method as claimed in any one of claims 1 to 8, wherein forming is performed integrally with the hot trimming without the use of holddown means to provide the wheel disc. Cutting the blank to be cut. A method according to any one of claims 1 to 9, characterized in that a blank composed of a composite material of manganese boron steel, multi-phase steel or multi-layer steel is hot formed to provide the wheel disc. And how to. A device for manufacturing a wheel disc (1) from a blank (6), said device being suitable for performing hot forming of said blank (6) to provide said wheel disc (1), It has at least one punch (7) and at least one die (8) for hot forming, and heat for introducing at least one opening (3,4,5) into the blank (6). In a device, provided with means (9, 10) for performing inter-room trimming,
At least one trimming bolt (9) and at least one corresponding application bolt (10) are provided,
The applicable bolt has at least one region (10a) having a cross-sectional shape in which the diameter gradually decreases toward the distal end side in the longitudinal direction of the applicable bolt (10),
Means are provided for adjusting the opening using the region (10a) of the applied bolt (10) having a varying cross-sectional shape,
The edge of the at least one opening (3,4,5) is plastically deformed and compressed between the at least one region and the at least one punch, thereby compressing the at least one opening. An apparatus characterized in that a portion other than the formed portion is plastically deformed to be thickened . Device according to claim 11, characterized in that at least one application bolt (10) is hollow so that the corresponding trimming bolt (9) can penetrate into the application bolt. Device according to claim 11 or 12, wherein the trimming bolt (9) and the application bolt (10) create a wheel bolt hole (4), a vent hole (5) and/or a wheel hub hole (3). The device is provided for the purpose. Device according to any one of claims 11 to 13, wherein at least one trimming bolt (9) is arranged such that the trimming bolt penetrates into the corresponding application bolt (10) from above. A device characterized by. The device according to any one of claims 11 to 14, wherein a trimming bolt (9) and an application bolt (10) are connected together with a movement path of the punch (7) and/or the die (8) to control movement. A device characterized in that it is provided with means for doing so. Device according to any one of claims 11 to 14 , wherein means are provided for separately controlling movement of the trimming bolt (9), the application bolt (10), the punch (7) and/or the die (8). A device characterized by being provided.

Images